Theoretical study on shear stress generated by microstreaming surrounding contrast agents attached to living cells.

Numerical calculations have shown that shear stress associated with microstreaming surrounding encapsulated stable bubbles of contrast agents, near living cells driven by 0.12-MPa acoustic pressure amplitude ultrasound (US) at 1 MHz or 2 MHz, may be large enough to generate reparable sonoporation of the cells. Some encapsulated bubbles that have mechanically weak shells may break into free bubbles under the above-mentioned sound field. When that happens, the shear stress caused by microstreaming surrounding the free bubble increases dramatically and may play an important role in lethal sonoporation and fragmentation of cells during the early stage of US exposure.